Date expressions

This section covers date expression evaluation rules.

A date expression evaluates to a DATE data type value.

MAIN
  DEFINE r, c DATE
  LET c = TODAY + 4
  LET r = ( c - 2 )
END MAIN

The operands of a date expression can be one of:

• A character string literal that can be evaluated to a date based on the DBDATE environment variable.
• A variable or constant of type DATE.
• A function returning a single date value.
• A unary + or - sign associated with an integer expression representing a number of days.
• The TODAY constant.
• A CURRENT expression with YEAR TO DAY qualifiers.
• An EXTEND expression with YEAR TO DAY qualifiers.

If a date expression includes an operand whose value is not a date data type, the runtime system attempts to convert the value to a date value following the data conversion rules.

If an element of an date expression is NULL, the expression is evaluated to NULL.